1. Field of the Invention
The present invention relates to position measurement sensors, and more specifically, it relates to a small, non-contact optical sensor using ranging and imaging to detect the relative position of an object in up to six degrees of freedom.
2. Description of Related Art
Presently, flexible manufacturing operations waste much time and money when changes have to be made in the manufacturing process. For example, if a minor modification is made to the shape of a car body and a robot is used to weld that body, the robot must be "taught" the new shape by an operator. That is, the operator must guide the robot tool by hand through each motion and every orientation in the welding operation. Besides being time consuming, this process is often inaccurate. It is also expensive because this is down time for both the robot and the operator. Furthermore, every part must be positioned exactly where the robot expects it to be, requiring the use of expensive sensors and positioning devices.
Many companies make non-contact laser sensors. Most are one dimensional (1D) range detectors, a few construct a 3D profile of an object, but the object must move through a fixed laser beam. By scanning a laser beam, a laser range camera can detect all three positions of a stationary object, but it does not detect orientation. Laser coordinate measuring systems (laser trackers) also detect three positions of a stationary object, but, made for large work volumes, they are too big (&gt;1 ft.sup.3) and too expensive (.about.$150,000) to mount on a robot or machine head.
U.S. patent application Ser. No. 08/719,061 describes a six degrees of freedom (SixDOF) optical sensor which utilizes a reflective dot and bar on an object, with a single light source, and optics to divide and manipulate reflections onto three photodetectors.